The present invention relates to fracturing operations and, more particularly, to methods of enhancing well productivity in propped fractures in portions of subterranean formations in weakly consolidated or unconsolidated formations.
Hydrocarbon producing wells are often located in subterranean zones that contain unconsolidated particulates (e.g., formation sand and fines) that can migrate with oil, gas, water, and other fluids produced by the subterranean formation. The presence of particulates in the production fluids is generally undesirable as they can cause abrasive wear to components such as screens, tubing, pumps, and valves. In some scenarios, particulates can clog the well, thus creating the need for expensive remedial treatments. If the particulates are carried to the surface, they may have to be removed from the production fluid using surface processing equipment.
The recovery of production fluids from weakly consolidated or unconsolidated formations can be enhanced by certain stimulation techniques. For example, hydraulic fracturing can create high-conductivity communication with a large area of a formation and bypass damage that may exist in the near-wellbore area. Hydraulic fracturing is a technique in which fractures are propagated in a rock layer for the eventual purpose of extracting certain fluids such as petroleum, natural gas, coal seam gas, and the like. The technique can be used to increase or restore the rate at which these fluids can be produced from a subterranean formation.
Conventional methods for preventing the production of particulate materials during fracturing operations include, for example, gravel packing the well adjacent to the weakly consolidated or unconsolidated production interval. A sand control screen (or “gravel-pack screen”) is a filter assembly that can be used to support and retain the sand placed during a gravel pack operation. Typically, the sand control screen is lowered into a wellbore on a work string and positioned relative to the desired production interval. Next, a fluid slurry that includes gravel is pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
In some cases, the processes of hydraulic fracturing and gravel packing can be combined into a unified treatment that can stimulate production while providing an annular gravel pack for sand control. Such treatments are often referred to as “frac-pack” operations. Frac-pack operations may be conducted with a gravel pack screen assembly in place, by pumping the fracturing fluid through an annular space between the screen and casing (or between the screen and the walls of the well bore, in “open hole” wells that are completed without casing). One of the goals of frac-packing operations is to create short, wide, highly conductive fractures and then to pack the area between the screen and the perforated casing or the inside wellbore surfaces (the “sandface”) by continually injecting slurry after the fracture has been filled with proppant and packed off.
A common method of creating short, wide fractures is to initiate a tip screenout during the pumping operation. In a tip screenout, the solids (e.g., proppants) concentration at the tip of the fracture becomes high due to fluid leak-off into the formation such that the slurry is no longer mobile. The concentrated proppant slurry plugs the fracture, preventing additional growth of the fracture length. Additional pumping of the proppant/fluid slurry into the formation after the screenout occurs causes the fracture to balloon. Therefore, a practical method of hindering the migration of formation sands and fines while inducing tip screenout in weakly consolidated or unconsolidated formations may be of value to one of ordinary skill in the art.